1. Field of the Invention
This invention relates to a novel liquid crystalline compound and a liquid crystal composition containing the same. More particularly it realtes to a liquid crystalline compound having an optically active group and a liquid crystal composition containing the same.
The liquid crystalline compound referred to herein includes not only those which can be observed to exhibit liquid crystal state by themselves, but also those which cannot be observed to exhibit liquid crystal state by themselves, but have a chemical structure similar to those of liquid crystal compounds and also have properties useful as a component for liquid crystal compositions.
2. Description of the Related Art
At present, TN (Twisted Nematic) display mode has been most broadly employed, but it is inferior in the aspect of response rate to emissive mode display elements such as electroluminescence display, plasma display, etc., and in this respect, various improvements have been attempted, but it does not appear that possibility of a notable improvement remains so much.
Thus, various attempts at liquid crystal display devices base on another principle in place of that of TN mode display element have been made, and as one of the attempts, there is a display mode utilizing ferroelectric liquid crystals (N. A. Clark et al; Applied Phys. lett., 36, 899 (1980)). This mode utilizes ferroelectric liquid crystal chiral smectic C phase (hereinafter abbreviated to SC* phase) or chiral smectic H phase (hereinafter abbreviated to SH* phase), and has the following three superior specific features as compared with TN display mode:
A first specific feature is that the mode has a very high response rate which amounts to 100 times those of TN display element. A second specific feature is that the mode has a memory effect, and the multiplex drive becomes easy coupled with the above-mentioned high-speed response properties. A third specific feature is that gray scale can be more easily obtained than TN display mode only by adjusting the inversion time of polarity; hence the mode has been considered as suitable for graphic display.
However, in spite of such superior specific features, currently known ferroelectric liquid crystals and compositions have not yet afforded fully satisfactory results in the aspect of response rate; thus it seems that they have come to deadlock in advance of practical utilization thereof. The reason may be said to consist in that development of compounds having a large spontaneous polarization value Ps has been late.